No. An interface with no methods is generally called a marker interface. And there's a lot of discussion about why marker interfaces are now considered a bad idea; you can find these using our search feature. Anyone calling this concept a "null interface" is creating needless confusion by using nonstandard, misleading terminology.
There's no actual term "null interface." What you might be referring to is a marker interface, which is indeed an interface defined with no actual methods to implement.
One of the most well-known examples is Serializable. When you implement Serializable, you do not have to actually implement any methods; you are simply telling the JVM that this class is allowed to be serialized. Another example is the Java 5 addition RandomAccess, which is implemented by ArrayList (and other classes) to signify that it provides effecient ( O(1) ) access to its elements.